Portable transponders, such as Radio Frequency Identification (RFID) tags, usually comprise one or more semiconductor chips for processing and storing data and an antenna for communicating with external devices, such as readers or “interrogators” and, via such readers, with other parts of supporting infrastructure. Typically, a transponder (hereinafter referred to simply as a “tag”) is provided with a unique identifier (UID) assigned from a global numbering scheme. A tag may also have sensing capabilities, such as being provided with a sensor for detecting temperature, pressure etc.
Tags usually communicate with readers using radio waves propagating through, for example, air. However, other parts of the electromagnetic spectrum may be used, such as optical parts of the spectrum (e.g. visible or infra red regions), and other forms of signal propagation may be used, such as acoustic waves. The distance for interrogation varies from few millimeters to several meters depending on the type of tag and reader, frequency, media, antenna, interferences and other factors. Depending on their technical characteristics, RFID readers can concurrently interrogate many tags in quick sequence, for example several per second, usually in a round-robin approach.
Typically, RFID tags interact with readers which are interconnected to identification and actioning systems comprising a data network and computers running appropriate software. Herein, such identification and actioning systems are referred to as “RFID systems”. These systems can trigger or perform a given action upon detection of a predetermined event. Examples of such actions include triggering replenishment transactions when stocks are reduced after object removal, firing an alarm upon temperature rise, or adding an item to the shopper's bill when they reach a till. RFID tags and supporting infrastructure (e.g. readers, data network and computers) provide an integral system for identifying and controlling objects and their environment. Neither the tag, nor the supporting infrastructure work in isolation. Therefore, within an RFID system, tags and the supporting infrastructure interoperate through, for example, standardisation of frequencies, protocols, interrogation procedures and numbering schemas and standardisation of protocols for the exchange of object identification and data.
In recent years, the use of RFID systems is becoming increasingly widespread. For example, RFID tags are attached to goods and products and these are managed by reading and writing information to and from the tags. This allows objects to be identified, tracked and traced, and their environmental conditions to be monitored.
RFID systems are employed in variety of fields such as manufacturing, logistics and distribution, amusement, rental and leasing. They can be applied, for example, in factories to manage the products or production materials being conveyed on a belt-type conveyor, in airports to manage baggage and in retail to track groceries. Leading manufacturers, distributors and retailers are promoting the use of RFID tags to replace barcode-based product identification procedures, to improve the visibility of their stock and to automate their operations.
RFID tags may be “passive”, i.e. they have no internal energy source and obtain energy for their reply from the interrogation field, or they may be “active”, i.e. contain an internal energy source, for example a battery. Tags usually reply only when they are within or have recently passed through an interrogation field. The interrogation field may function to select a single tag among a population of such tags, to issue a generic interrogation aimed at all the tags within the interrogation field, to issue a semi-generic interrogation aimed at some of the tags within the interrogation field, and/or, in the case of passive tags, to provide energy, a portion of which may be used in constructing the reply. Passive tags are described in U.S. Pat. No. 3,713,148.
Typically, RFID tags respond to interrogations by transmitting their UID and, optionally, other data. Some tags can communicate using encryption mechanisms, for example as described in US-A-2005/017844 and WO-A-2005/027022, although most tags, particularly passive tags, have no security or encryption mechanisms. In particular, the prohibitive cost of RFID tags with encryption capabilities hinders their usage in the tagging of fast moving consumer goods (FMCG) and other low-cost or low-margin objects. Moreover, due to cost efficiencies and security reasons, RFID tags in FMCG are usually “embedded” into the packaging or product itself, hence impeding or complicating their removal. More importantly, most RFID systems used in the control of FMCG typically reply overtly to generic or semi-generic interrogation from compatible readers, these are usually referred to as “talkative” tags.
For these reasons, adoption of RFID systems for the tracking of FMCG and other goods is facing significant opposition from privacy advocates and regulators because their usage might allow spying on consumers and exposing them to theft. For example, talkative tags can be interrogated by unauthorised parties through clothing, when in pockets or hand bags, and even through thin walls. Moreover, some RFID global numbering systems include the product type within their codification structure, so revealing important product characteristics such as product nature, price etc.
Consequently, some RFID advocates propose the removal or disabling of tags at the Point Of Sale (POS) and reference is made to US-A-2006/061475. However, this option has been rejected by some privacy advocates because the process is cumbersome, unreliable and hinders valuable post-POS applications, such as domestic applications, automatic recycling etc.
Similarly, temporary deactivation of tags may not satisfy privacy concerns. RFID protocol proposals include a kill command that renders the tag inoperable. This kill command is often referred to as a “Privacy” command, which can be used to permanently deactivate the device at the end of its working life, for example as a customer leaves a store. However, there are two problems associated with the kill command. Firstly, the execution of a kill command is only protected by a short password, for example 8 bits long. Organizations using RFID tags are therefore concerned that unauthorized people may be able to deactivate them even before point of sale. Secondly, privacy advocates are afraid that the kill command may not permanently “destroy” a tag. The entity that made the tag may also have means to reactivate it.
The present invention seeks to provide a method of and apparatus for tracking an object tagged with a radio frequency identification tag which is privacy friendly.